The invention relates to opening aids for ampuls, which ensure a reliable and safe opening of ampuls and at the same time facilitate quick transfer of ampul content, without loss, into a vessel, which may be, for example, a volumetric flask or a beaker.
The ampuls under consideration are in particular plastic ampuls containing concentrated solutions for the preparation of volumetric, standard and buffer solutions. Probably the best known opening aids for these ampuls are glass rods. With respect to equipment safety laws, glass rods are implements which entail considerable risk of injury. When using the typical glass rod of up to 30 cm long, the rod may break impaling the hand holding the rod on the resulting splintered glass stub.
A further development is the plastic-sheathed glass rod; however, these rods have a number of disadvantages, i.e., the behavior of water and aqueous solutions as they drain off these rods is unfavorable; the sheathing may become detached at the glass/plastic interface, and plastic sheathed glass rods are disproportionately expensive.
Plastic and metal rods cannot be used repeatedly due to their resistance to cleaning agents used in volumetric analysis (ethanolic potassium hydroxide solution or chromic-sulfuric acid). Moreover, a metal rod must also not be used in the field of trace analysis of metals, in that the metal will contaminate standard solutions.
Another opening aid for ampuls currently on the market is a special plastic knife: however, this aid has the following disadvantages: loss of the ampul content because the knife cannot be rinsed; loss of the ampul content when turning around an ampul opened on one side; and if the volumetric flask is fitted onto the ampul before turning it around and both are turned around together, the volumetric flask may break. In addition, if the opening on the end of the ampul is too small, the content runs out very slowly and rinsing out the ampul is difficult.
Although an opening aid for ampuls closed by plastic membranes is described in German Offenlegungsschrift No. 3,531,071, the embodiment still has a number of disadvantages in that, to open the ampul, the membrane has to be pressed in from outside. As the membrane cannot be removed completely in this way, a dead volume occurs behind the pressed-in membrane, in which liquid collects that cannot be rinsed out completely. A quantitative rinsing out is therefore not ensured. The liquid also has to flow out via an inner tube, the diameter of which must, of course, be smaller than the ampul neck itself. Between the two tubes there is a dead volume, which makes a quantitative rinsing out impossible. Welding of the cutting edge to the membrane, as proposed in German Offenlegungsschrift No. 3,531,071 is likewise not a satisfactory solution to the problem in that welding causes holes to occur in the membranes in a high proportion of the ampuls. Moreover, the opening which can be achieved by spot-welding of the cutting edge is very small, so that a quick flow of the content out of the ampul is impossible.